1. Field of the Invention
The present invention relates to a polytetrafluoroethylene (PTFE) stud for mounting an ultrahigh-value resistor whose characteristics may change due to soldering-induced heat.
2. Description of the Related Art
Ultrahigh-value resistors typically have a resistance of several giga-ohms to several tera-ohms. Known examples include what is disclosed in http://www.hydrazine.co.jp/e_c/pdf/j-pdf/j-rh-u.pdf and http://www.hydrazine.co.jp/e_c/pdf/j-pdf/j-ru.pdf found at http://www.hydrazine.co.jp/e_c/jpn/j_teiko.html.
Those ultrahigh-value resistors are used for, for example, a measuring instrument to detect a micro current. Resistance errors have a large influence on the measurement accuracy. Resistance errors may be caused by, for example, temperature changes. Those ultrahigh-value resistors have an internal structure that is susceptible to thermal stress. Thus, when the ultrahigh-value resistors are mounted by soldering, a shock due to the soldering-induced heat, i.e., thermal stress applied in a short period of time, may render the resistance unstable.
Accordingly, even when a user performs inspection and/or adjusts the value after the manufacture of the measuring instrument, he or she needs to fully allow for the error which otherwise may affect the measurement accuracy of the instrument. Thus, measures, such as mitigating thermal shock or thermal stress by temporarily attaching a heat-dissipating jig to the lead of the ultrahigh-value resistor, have been taken during the soldering of the resistor.
Examples of related art include a stud product, using PTFE (e.g., Teflon®) material, for a printed circuit board and for surface-mounting a PTFE terminal manufactured by Mac Eight Co., Ltd. (2004a159.pdf (http://www.mac8sdk.co.jp/item/teflon_smt/fh.html) and 2004a220.pdf (http://www.mac8sdk.co.jp/item/teflon/fx.html)). In addition, Japanese Unexamined Patent Application Publication No. 2002-8759 (Document 1) discloses a PTFE terminal having a plurality of grooves.
However, the method for mitigating thermal shock by attaching the above-noted heat-dissipating jig has problems in that, for example, the process and procedure for mounting a component become complicated and subsequent maintenance work does not allow soldering. The above-noted stud product using PTFE material requires high insulation between the substrate and the terminal and is not adapted to reduce thermal transmission. Document 1 discloses a technique using PTFE for a highly-insulating stud, and the technique is intended to reduce the area occupied on the substrate and to improve the work efficiency. Document 1, however, does not disclose a technique for reducing thermal transmission.
In a micro-current measurement apparatus, an ultrahigh-value resistor is often air-wired, i.e., wired away from the substrate, with a supporting member interposed therebetween, and application of soldering-induced thermal shock to the ultrahigh-value resistor causes a variation in resistance.